For many applications regarding the generation of an electric field in an aqueous medium, electrodes are typically placed directly in an aqueous buffer solution and connected to an external power source to form an applied voltage difference. If the applied voltage exceeds about one volt, as is typical in electrophoretic and electroosmotic applications, the applied voltage causes electrolysis of water. The electrolysis results in the generation of hydrogen gas at the cathode (negative electrode) and oxygen gas at the anode (positive electrode).
Problems exist in operating microchannel devices and other integrated devices for sequencing or concentrating biomolecules because of the need for a connection to an external source of current, usually a high-voltage power supply. Conventionally, such connections are made by dipping a wire, such as a platinum wire, in small containers filled with an electrolyte buffer solution. Generated hydrogen gas bubbles and oxygen gas bubbles resulting from electrolysis are vented or escape to the atmosphere.
In many devices that include an electrochemical cell, the formation of bubbles at one or both electrode surfaces can create serious problems. These devices include microbiological analytical devices, microelectrophoretic devices, bulk flow transport systems, and devices where electrodes must be placed in confined or sealed fluidic channels. Interfacing of such devices with the electrodes creates particular problems. Among these problems are siphoning, evaporation of electrolyte, excessive current path lengths and associated heating requirements, excessively complex electromechanical systems and configurations, excessively large systems and electrolyte reservoirs, excessive reagent and/or electrolyte consumption, and in some cases the impossibility of placing electrodes driven by DC or low frequency AC current inside channels or closed chambers.
Palladium has been used as an electrode material in electrophoretic devices, for example, the electrophoretic devices described in U.S. Pat. No. 5,833,826, which is incorporated herein in its entirety by reference. In addition, it is well known that palladium absorbs hydrogen. However, palladium does not absorb oxygen gas generated at the positive electrode of an electrochemical cell rendering it undesirable as an electrode material in microbiological analytical devices, microelectrophoretic devices, bulk flow transport systems, and devices where electrodes must be placed in confined or sealed fluidic channels.